The ancient, prototype nuclear plant (the ones installed all over the western world in the 1950's and 1960's) DO require the very same enrichment cycle that nuclear weapons require.
Sorry, wrong. The current light water reactors in the US run on up to 5% enriched U-235 (and cannot use anything higher due to regulation). For nuclear weapons it takes over 20% at least, usually over 90%. http://en.wikipedia.org/wiki/Enriched_uranium
If you can't understand it, it is intuitively obvious.